Bottom Anti-Reflective Coatings (BARC) are known in the art for improving photolithography processes. In Back Side Illumination (BSI) image sensors, various subsequent processing steps can damage a BARC film.
By way of example, if an etching process to remove an overlying buffer oxide layer continues into the BARC film, the BARC film may be damaged. The damage to the BARC film may undesirably induce a high leakage current in the image sensor.
As another example, if the etching process to remove the overlying buffer oxide layer stops prior to reaching the BARC film, some of the undesirably remain. The remaining buffer oxide may have an undesirable thickness and/or a poor uniformity, which may degrade the optical performance of the image sensor. In other words, the buffer oxide overlying the BSI image sensor array is not fully removed, the quality factor (QE) and/or signal to noise ratio (SNR) of the resulting sensor device can be degraded.
Corresponding numerals and symbols in the different figures generally refer to corresponding parts unless otherwise indicated. The figures are drawn to clearly illustrate the relevant aspects of the embodiments and are not necessarily drawn to scale.